Chelsea were poor against Manchester United, very poor. That for the first time in a decade they did not manage a shot on target is damning. And it is true that they have not of late been playing with the relentlessness they did through the final three months of last year. But the idea they were somehow been found out on Sunday seems weirdly exaggerated. The title race may be on again but Chelsea have a lead of four points over Tottenham, whatever psychological pressure Spurs may be able to apply in Saturday’s FA Cup semi-final.

In terms of shape, Chelsea have had two major strengths since making the switch to 3-4-2-1 after the defeat to Arsenal in their sixth Premier League game of the season. The back three, shielded by N’Golo Kanté and Nemanja Matic, have presented a solid block and has allowed David Luiz to utilise his greatest assets, his strength and passing ability, without exposing his biggest weakness, his positional sense.

Eden Hazard and Pedro, operating in effect as inside-forwards, have been able to exploit the awkward pockets that exist between the opposing holding midfielders and full-backs. José Mourinho is not the first to see the best way of countering the pair as being to use three central defenders, so one can always step out to meet the opponent with the knowledge the other two are covering. For those who see the game primarily in positional terms, which Mourinho probably does not, it is the obvious solution.

All three of the coaches working in the Premier League who were at Barcelona when Louis van Gaal was in charge in the late 90s have a grounding in juego de posición and have tried the back three against Antonio Conte’s side. First was Ronald Koeman but Everton were beaten 5-0 in November. Then came Pep Guardiola but Manchester City, despite being the better side for almost an hour, lost 3-1 a month later.

Mourinho simply applied the same logic but with a greater emphasis on defence and with greater resolve. Eight teams have played a back three against Chelsea this season. Six have lost. Recognising a solution and being able to enact it are not the same thing.

There were other issues beyond United’s defensive excellence. Ander Herrera did a fine job of marking Hazard, who is so key to Chelsea’s attacking approach he has created 66 chances this season, 25 more than any of his team‑mates. Other sides may be tempted to follow the Herrera model and man-mark Hazard, although for teams used to playing zonally, losing a midfielder to such a specific task can be disorienting. Hazard, anyway, may not seem quite so bereft when he has Marcos Alonso back as the left wing‑back, offering a familiar option outside him.

Would Thibaut Courtois have been quicker off his line than Asmir Begovic to meet Marcus Rashford when he scored United’s first goal? If Mourinho’s side had not taken a seventh-minute lead would they have been able to play as reactively as they then did? Just as the early goal shaped the league meeting at Stamford Bridge, when Chelsea won 4-0 in October, so it influenced Sunday’s game. If Chelsea are minded to look for excuses or explanations, they are readily found. The bigger concerns with regard to the title run-in are the fact they have not kept a clean sheet in the past 10 Premier League matches and Diego Costa’s loss of form.

Yet in a sense, whatever formula Mourinho has devised, however many others may employ it, is academic for Saturday’s FA Cup semi-final.

Tottenham’s Mauricio Pochettino was the first manager to lead his side to a league victory over Chelsea after their switch to a back three. He too deployed three at the back in that 2-0 win at White Hart Lane in January, in effect matching Chelsea shape-for-shape by fielding Dele Alli and Christian Eriksen behind Harry Kane.

Spurs seemed quicker, stronger and sharper than Chelsea, winning the battle in midfield, where Mousa Dembélé and Victor Wanyama bested Kanté and Matic, and on the flanks, where Kyle Walker and Danny Rose forced Victor Moses and Alonso on to the back foot, exposing a defensive weakness with deep crosses to the back post. If that did not offer a blueprint to other sides facing Chelsea, why should United’s win?

On form – and assuming Tottenham can overcome whatever hex it is that prevents them playing well at Wembley – there is no reason why they should not repeat that result from January.

Perhaps that will increase the psychological pressure on Chelsea, as Kane has suggested it may. If Conte’s side do stumble in the run-in, it will be far more down to anxiety than because teams have suddenly worked out that a back three is an effective way to counter them.